The Nanopyramidal Reconstruction of Cu 2 O(111): a Long-standing Surface Puzzle Solved by STM and DFT

A. Gloystein (1) , N. Nilius (1) , J. Goniakowski (2, 3) , C. Noguera (2)

1 OFFIS - Carl Von Ossietzky Universität Oldenburg = Carl von Ossietzky University of Oldenburg
2 INSP - Institut des Nanosciences de Paris
3 INSP-E9 - Oxydes en basses dimensions

Despite the importance of cuprous oxide for industrial applications, the precise structure of its most stable reconstructed surface remains unknown. Here, by a combination of highresolution STM measurements and simulations based on a DFT-HSE approach, we challenge the previous interpretations of the Cu 2 O(111) (√ 3× √ 3)R30 • surface reconstruction, based on the removal of 1/3 of the under-coordinated surface oxygen atoms. We show that these models do not satisfy the shamrock-type features found by STM, i.e. their position in the Cu-O ring centers, the orientation towards the surface O cus atoms and the topographic height in the STM images. Moreover, they are thermodynamically unstable with respect to moving the vacancy subsurface, a property not recognized before which seems specific to the Cu 2 O (111) surface. We propose a nanopyramidal model of the (√ 3× √ 3)R30 • surface reconstruction which is free from all these shortcomings. Here, the shamrock protrusions seen in STM are formed by three copper adatoms located at the center of the Cu-O rings and capped by an oxygen atom. This structure profoundly differs from existing models of the Cu 2 O(111) surface, and would change common perceptions on its reactivity.

Mots clés: Copper; Ions; Oxygen; Defects in solids; Scanning tunneling microscopy

Domaines: Physique [physics]

A. Gloystein, N. Nilius, J. Goniakowski, C. Noguera. The Nanopyramidal Reconstruction of Cu 2 O(111): a Long-standing Surface Puzzle Solved by STM and DFT. Journal of Physical Chemistry C, 2020, 124 (49), pp.26937-26943. ⟨10.1021/acs.jpcc.0c09330⟩. ⟨hal-03182387⟩